Piston of refractory materials, particularly for compression-ignition engines

Abstract

A piston (2) is of refractory materials, particularly for a compression-ignition engine of the type having a head (4), a skirt (6) and their mutual fastening means. According to the invention, this skirt (6) is formed entirely of a refractory material and has two semicylindrical parts (18, 20) each of which has ribs (22) and a semispherical cavity (36, 38). After assembly, the cavities form a ball joint seat for the small end of a piston rod along a plane containing the longitudinal axis (14) of the piston (2). Application is to compression-ignition engines with high efficiency.

What is claimed as new and desired to be secured by Letters Patent of the United States is: 
     
       1. A piston comprising: a cylindrical piston head formed entirely of a refractory material having low coefficients of thermal expansion and conduction, said piston head having a longitudinal axis and first and second end faces;   a combustion chamber formed by a recess in said first end face of said piston head;   a plurality of recesses circumferentially distributed about said longitudinal axis of said piston head and opening on said second end face of said piston head;   a cylindrical piston skirt formed entirely of refractory material having low coefficients of thermal expansion and conduction, said piston head having a longitudinal axis and first and second end faces;   means for coaxially securing said second piston head face and said first piston skirt face to one another;   a plurality of ribs formed on a peripheral surface of said skirt; and   a spherical cavity in said piston skirt, said spherical cavity intersecting said skirt longitudinal axis and opening on said second end face of said skirt, whereby said spherical cavity may receive a small end of a piston rod,   wherein said piston skirt is formed of two semi-cylindrical skirt halves assembled into said skirt at mutually contacting surfaces defining a plane containing said skirt axis, each of said skirt halves including said ribs and a semi-spherical half of said spherical cavity.   
     
     
       2. The piston of claim 1 including means for assembling said skirt halves into said piston skirt, wherein said means for coaxially securing said second piston head face and said first piston skirt face comprise: first bores in said skirt and head and extending coaxial with said longitudinal axes;   a threaded insert in each of said first bores;   a fastening screw in each of said first bores, each said fastening screw being threaded to one of said inserts;   wherein said means for assembling comprise:   said means for coaxially securing said second piston head face and said first piston skirt face;   second bores in each of said skirt halves and extending transverse to said longitudinal axes; and   centering rings in said bores, each centering ring crossing said plane.   
     
     
       3. The piston of claim 1 or 2 including thermally insulating fiberous material filling each of said recesses in said piston head. 
     
     
       4. The piston of claim 1 or 2 wherein said piston head is made entirely of a material having good compression strength. 
     
     
       5. The piston of claim 4 wherein said piston head is formed entirely of sialon ceramic material. 
     
     
       6. The piston of claim 1 or 2 wherein said piston skirt is made entirely of a material having a low coefficient of friction, and having good compression and bending strength. 
     
     
       7. The piston of claim 6 wherein said piston skirt is formed entirely of silicon nitride ceramic material. 
     
     
       8. The piston of claim 1 or 2 wherein said piston skirt has a smooth peripheral surface lacking a sectioning groove. 
     
     
       9. The piston of claim 1 or 2 wherein said peripheral surface is an external peripheral surface.